Reciprocal ferrite phase shifter having means detecting deviations of the energy from desired linear polarization

ABSTRACT

A ferrite phase shifter having a pair of nonreciprocal circular polarizers with a nonreciprocal phase shifter between them, including an electronic control for altering the magnetization of the nonreciprocal circular polarizers. This arrangement may be used to compensate for temperature and power changes and may provide a bandwidth substantially equal to the theoretical for a ferrite loaded waveguide of the same configuration. In the preferred embodiment the waveguide is square, the nonreciprocal circular polarizer (NRCP) is of the transversely magnetized quadrupole field type, and electronically controllable electromagnets at each corner of the NRCP sections provide the required level of magnetization to maintain accurate 90* phase shift of orthogonal vector components of the propagating electromagnetic wave. Also in the preferred embodiment, a linear polarizer at one end of the phase shifter includes a resistive film, and a detector diode is attached to the film to detect deviations of the propagating wave from the desired linear polarization. The detector diode is a part of a control circuit which adjusts the NRCP control magnet settings.

United States Patent Safran Aug. 14, 1973 OF THE ENERGY FROM DESIRED LINEAR POLARIZATION 75] Inventor: Paul Safran, St. Louis, Mo.

[73] Assignee: Emerson Electric Co., St. Louis.

[22] Filed: Apr. 20, 1972 [21] Appl. No.: 245,847

[52] US. Cl 333/17, 333/21 A, 333/31 A [51] Int. Cl. H03h 7/16, HOlp 1/18 [58] Field of Search 333/17, 21 A, 24.1, 333/31 R, 31 A [56] References Cited UNITED STATES PATENTS 3,081,438 3/1963 Levy 333/17 3,626,335 12/1971 Hord et al 333/31 A OTH ER PUBLICATIONS Boyd, Jr., A Dual-Mode Latching Reciprocal Ferrite Phase Shifter, IEEE Trans. on MTT, Dec. 1970, pp. 1,1 l91,124

Primary Examiner-Paul L. Gensler Attorney-Philip B. Polster and J. Philip Polster [57] ABSTRACT A ferrite phase shifter having a pair of nonreciprocal circular polarizers with a nonreciprocal phase shifter between them, including an electronic control for altering the magnetization of the nonreciprocal circular polarizers. This arrangement may be used to compensate for temperature and power changes and may provide a bandwidth substantially equal to the theoretical for a ferrite loaded waveguide of the same configuration. 1n the preferred embodiment the waveguide is square, the nonreciprocal circular polarizer (NRCP) is of the transversely magnetized quadrupole field type, and electronically controllable electromagnets at each corner of the NRCP sections provide the required level of magnetization to maintain accurate 90 phase shift of orthogonal vector components of the propagating electromagnetic wave. Also in the preferred embodiment,

a linear polarizer at one end of the phase shifter includes a resistive film, and a detector diode is attached to the film to detect deviations of the propagating wave from the desired linear polarization. The detector diode is a part of a control circuit which adjusts the NRCP control magnet settings.

15 Claims, 5 Drawing Figures r ".2 l i K T l l4 e i J K) 45 (V DRIVER DETECTOR CIRCUIT CIRCUIT l 29 39 COMPUTER -COMPU-TER SCAN a EIRECTOR 1 25 1 DRIVER CIRCUIT v 5:

L37 FREQUENCY Patented Aug. 14, 1973 3,753,160

2 Sheets-Sheet l I 4 PHASE SHIFTER 2 LINEAR POLARIZER NON RECIPROCAL LINEAR POLARIZER CIRCULAR POLARIZER FIG. I.

MAGNETIC omsc'r PLATING FIG.2.

FERRITE ROD 2 Sheets-Sheet 2 FIG.3. 9

. (5%; J 45 H v DRIVER DETECTOR 27 CIRCU CIRCUIT I [v 9 COMPUTER COMPUTER SCAN DIRECTOR DRIVER CIRCUIT v s: V

c. FREQUENCY GENERATOR LEAD P ss N i CONTROL con.

7 ,5 CERAMIC PLATiNG REslsTw FILM FERRITE FlG.5.

nets, and other ferrimagn'etic materials are meanttobe'.

included.

Electromagnetic wave phase shifting devices, particularlyferrite devices, are well known. one suchferrite phase shifter includes a waveguide which is loaded in part withan'axially magnetized ferrite andwhich also includes in the waveguide a circular polarizer. The circular polarizer convertsan incident linearly polarized wave'to a circularly polarized wave, and thephase shift imparted to the wave is dependent onthe levelof magnetization of theaxially magnetized ferrite. Thislevel is typically controlledby a control winding. Aparticularlydesirable ferrite phase shifter utilizes nonrecipro cal circular polarizers (NRCPs) at both axial ends'of the axially magnetized phase shift section andlinear polarizers axially beyondthe circular p'olarizer sec tions. Thisarrangement allows the phase shifter to be reciprocal,and the addition ofthe'ferrite yokepermits latching operation of the phaseshifter. This type of phase shifter is'described; for example, in an article'by Boyd in IEEE Transactions onMierowaveTheoryand Techniques, December, 1970, pages lll9-24 and in Hord and BenetUS: Pat. No. 3,626,335. An exactly analagous reflective deviceomits one circular polarizer and includes instead ar'eflectivetermination'at one end of the phase shiftsection.

Although thetype of ferrite phase shifter described has numerous recognized advantages, its bandwidth, even utilizing the transversely magnetizedquadrupole field type NRCPs and'a square waveguide, is limitedto about 20 percent. Beyond this, insertion losses become excessive. The device is also sensitive to heat and to changes in power level of the propagating electromagnetic wave. Furthermore, the insertion losses caused by any of these factors appear as heat in the linear polarizer sections andthis heat further degrades the performance of the phase shifter and increases insertion losses; Therefore, under some extreme conditions (or a combination of adverse eondition'slthe device may" avalanche.

SUMMARY OF'THE INVENTION in the art inlight of the following description and accompanying drawings.

In accordance with this invention, generally stated, a phase shifting device for use in an electromagnetic wave transmission or reflection system is provided comprising waveguide means, first magnetic means in the waveguidefor converting applied linearly polarized wave energy into substantially circularly polarized energy andphase shifter'means including second magnetic means inthe waveguide'for effectinga controlled phaseshift of the circularly polarized wave energy, and further comprising control means for controlling the magnetization of the firstmagnetic means' and circuit means for energizing the controlmeans. The circuit means comprise variable means for chahging'the magnetization inresponse toa change ina condition tending todegrade the conversion from linear to circular polarization. Preferably, the device is of the transmission type and thirdmagnetic meansare provided in the waveguide for convertingthe phase shifted circularly polarized wave energy to linearly polarized wave energy, the-phase shifter being disposed between the first and thirdmagnetie meanspThe two circular polarizers are preferably of the transversely magnetizedquadrw pole fieldtype; The magnetic means of such polarizers may be'the ends of the same ferrite rod utilized in the phase shiftermeans and may be controlled by coils and field pieces arranged about the circular" polarizers. Preferably the variable means in the controlcircuit inelude a sensor in thewaveguide for sensing a variation from adesired polarization. Preferably, linear polarizersincluding resistive films are positionedin the waveguideatthe'axialends of the waveguide for absorbing wave en'ergy polarized parallcl to the film, aridthe sensor is placed in or on the resistive film of one of thelinear polarizers. The sensor may be, for example, a heat or voltage sensitive diode. Also in the preferred embodimenta frequency to-control settingp'rogram automatically changes the NRC? settings when the frequency of waveenergy propagating through the device is changed. Also in the preferred embodiment the waveguideis plated directly onto square ferrite and ceramic pieces, and boththe NRCP and the phase shift means are latching. I I

In the drawings,FIG. l is a diagrammatic view in side elevation of a phase shifting device of this invention;

variations, which may operate more accurately and with less insertion loss than presently knownferrite phase shifters, and whichmay be constructed to lower tolerances than presently knownferrite phase shifters, if desired.

Another object isto provide such a phase shifter which may be reciprocal and latching, which may be FIG. 2 isa sectional view taken along the line 2--2 of FIG. 1;

FIG. 3 is a fragmentary view, in side elevation, partially diagrammatic, of the phaseshiftingdevice of FIG.

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 3; and

FIG. 5 isa sectional view taken alongthe line 55 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, reference numeral I indicates one illustrative embodiment of the phase shifter of this invention. The phase shifter l includesa phase shift section 3 having nonreciprocal circular polarizer sections 5 and 7 at its axial ends and having linear polarizers 9 and 11 axially beyond the circular polarizers 5 and 7. Phase shifter section 3 and nonreciprocal circular polarizer parts 5 and 7 are constructed of a single square rod 13 of ferrite material and the linear polarizers 9 and 11 include split square ceramic rods 15 of the same external dimension as the rod 13. A resistive film 17 is sandwiched or deposited between the halves of the split ceramic rods 15. These ceramic rods 15 are glued to the ends of the ferrite rod 13 to form a composite rod of uniform cross-section, and this rod is plated to form a waveguide, as shown at 19. The phase shifter section 3 also includes a control coil 21 wrapped around the waveguide 19 and a pair of axially extending magnetic yoke pieces 23 for imposing a desired axial magnetization on the phase shifter section of the ferrite rod 13 and for maintaining a remanent magnetization. This magnetization is changed by imposing a preselected pulse to the control coil 21. The setting of the phase shifter 3 is controlled by a computer 25 through a digital driver circuit 27. When the phase shifter is used in a phased array transmission system, the computer 25 simultaneously (or nearly so) sets the control coils of all of the phase shifters in the system in accordance with the instruction of a scan director 29 which is in part a programming and timing circuit and which may also include a manual scan control. This much of the phase shift device 1 is presently known.

Because of the broad band capabilities of the phase shifter 1, in this preferred embodiment the computer 25 is also connected to a frequency generator 31 to alter the phase shifter settings when the frequency generator 31 alters the frequency of the electromagnetic wave energy propagating through the phase shift device 1. These alterations of the settings are digitally preprogrammed for different frequency bands, and compensate for the frequency effects on the phase shift provided by a given magnetization.

The nonreciprocal circular polarizer sections 5 and 7 each include a set of four magnetic yoke pieces 33 and a control coil 35 wrapped about the magnetic yoke pieces 33 to form a controllable transversely magnetized quadrupole field. The yoke pieces 33 are made of magnetically permeable material to form latching yokes with the NRCP parts of the ferrite rod 13 when a control signal is imposed on the coil 35. The magnetic poles and resulting E and H fields are shown in FIG. 2. The coil 35 is controlled by a digital driver circuit 37 which in turn is controlled by a computer 39. The driver circuit 37 in this embodiment controls the windings 35 of both the nonreciprocal circular polarizers 5 and 7, although separate driver circuits may be provided if desired. The computer 39 may control all of the driver circuits 37 in a phased array transmission system. It is preferred that at least some of the computer functions be individual to each phase shifter, as described hereinafter.

One of the inputs to the computer 39 is from the frequency generator 31, to provide a fixed digital change in the remanent magnetization of all the NRCPs 5 and 7 for each change in the frequency band propagating through the phase shifters l.

The other input to the computer 39 is a feedback loop to maintain the desired 90 phase shift between orthogonal components of the propagating wave as the wave passes through the circular polarizer 5 or 7. In

this preferred embodiment, the feedback loop includes a detector diode 41 embedded in the resistive film 17 of the output NRCP 7. As is known, a vector component of the propagating wave parallel to the resistive film 17 is absorbed by the film 17. The resulting voltage induced across the diode 41 is converted by a detector circuit 43 into an error signal fed to the computer 39, which in turn initiates a hunting cycle in the driver circuit to reduce the voltage across the diode 41 to a predetermined threshold level. lt will be seen that the diode 41 could also be a heat sensitive device. The detector 41 and detector circuit 43 directly sense deviation of the output wave from the desired polarization. Although the sensor 41 could be used exclusively to control the NRCP settings, it is preferred to provide preset control programs to respond to discrete changes in variables such as frequency (e.g. the computer adjustment in response to changes in the frequency of the propagating wave energy), and to relegate the detector circuit 43 to a trimming function.

Because the insertion losses of the phase shifting device 1 caused by frequency or temperature effects are almost entirely due to the nonreciprocal circular polarizer sections of the phase shifter, and because the present invention provides virtually complete control of this section, these losses may be limited to any desired value by closely controlling the settings of the nonreciprocal circular polarizers 5 and 7.

The driver circuit 37 or computer 39 may also be utilized to compensate electronically for physical differences in the two nonreciprocal circular polarizers 5 and 7. Therefore, it is possible, if desired, to reduce the extremely close manufacturing tolerances normally required for a phase shifter of this general type.

By varying the settings of the nonreciprocal circular polarizers 5 and 7 with changes in frequency of the propagating electromagnetic wave energy, the desired polarity of the wave energy may be maintained accurately and insertion losses may be kept to a minimum across the entire frequency band (regardless of whether the phase shift section is frequency compensated). Therefore, the phase shifter may be utilized over the entire frequency range of the square filled waveguide, limited only by the onset of higher order modes. The bandwidth may be greater than 1.3:1 and may approach 2:1.

Numerous variations in the phase shifting device of this invention, within the scope of the appended claims, will occur to those skilled in the art in light of the foregoing disclosure. For example, other nonreciprocal circular polarizers utilizing other control means may be utilized. The waveguide may be round rather than square and may be a separate structural element rather than a mere plating directly on ferrite and ceramic elements. Where wide bandwidth is not critical, the use of a round ferrite-filled waveguide may be preferred, for ease of fabrication. A reflective phase shifter may be constructed merely by omitting the second NRCP 7 and linear polarizer 11 and plating the end of the rod 13 to make a reflective termination. In this case, the remaining NRCP performs the functions of both circular polarizers, and careful control of the polarization of incident wave energy is required for use of the detector diode 41. Two devices like the phase shifter 1 may be combined in a manner similar to that of the Hord et al. Pat. No. 3,626,335, to produce a phase shifting device which will handle any sense of polarization of the propagating wave. The phase shift section and the nonreciprocal circular polarizer sections may be analog controlled rather than digitally controlled and may be nonlatching. These variations are merely illustrative.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. In a phase shifting means for use in an electromagnetic wave system comprising waveguide means, circular polarizer means including first ferrimagnetic means in said waveguide means for converting applied linearly polarized electromagnetic wave energy into substantially circularly polarized wave energy, and phase shifter means including second ferrimagnetic means in said waveguide means and controllable means for magnetizing said second ferrimagnetic means axially of said waveguide means for effecting a controllable phase shift of said circularly polarized wave energy, the improvement comprising control means for controlling the magnetization of said first ferrimagnetic means, and circuit means for energizing said control means, said circuit means comprising variable means for changing said magnetization of said first ferrimagnetic means in response to a change in a condition tending to degrade said conversion from linear to circular polarization.

2. The improvement of claim 1 wherein said circular polarizer means comprise a transversely magnetized quadrupole field nonreciprocal circular polarizer.

3. The improvement of claim 2 wherein said variable means comprise preprogrammed means responsive to a change from one preselected wave energy frequency to another preselected wave energy frequency.

4. The improvement of claim 2 wherein said variable means are temperature responsive.

5. The improvement of claim 2 wherein said variable means comprise sensor means in said waveguide means for sensing divergence from a desired polarization of said wave energy.

6. The improvement of claim 5 including a linear polarizer on the side of said circular polarizer means away from said phase shifter means, said linear polarizer comprising absorptive means for absorbing wave energy polarized normal to a desired plane of polarization, said sensor means comprising means operatively connected to said absorptive means.

7. The improvement of claim 6 wherein said absorptive means comprise a resistive film and said sensor means comprise a diode in contact with said film.

8. The improvement of claim 2 wherein the waveguide is square in cross section.

9. The improvement of claim 2 wherein said first and second ferrimagnetic means comprise a single rod.

10. The improvement of claim 1 including second circular polarizer means including third ferrimagnetic means in said waveguide means for converting said phase shifted circularly polarized wave energy to linearly polarized wave energy, said phase shifter means being disposed between said first and second circular polarizer means.

11. The improvement of claim 10 wherein said first and second circular polarizer means comprise trans versely magnetized quadrupole field nonreciprocal circular polarizers.

12. The improvement of claim 11 wherein said control means control the magnetization of both said first and third ferrimagnetic means.

13. The improvement of claim 1.2 wherein said variable means comprise sensor means in said waveguide means for sensing divergence from a desired polarization of said'wave energy.

14. The improvement of claim 13 including a linear polarizer on the output side of said second circular polarizer means, said linear polarizer comprising absorptive means for absorbing wave energy polarized normal to a desired plane of polarization, said sensor means comprising means operatively connected to said absorptive means.

15. The improvement of claim 151 wherein said first, second and third ferrimagnetic means comprise a single rod. 

1. In a phase shifting means for use in an electromagnetic wave system comprising waveguide means, circular polarizer means including first ferrimagnetic means in said waveguide means for converting applied linearly polarized electromagnetic wave energy into substantially circularly polarized wave Energy, and phase shifter means including second ferrimagnetic means in said waveguide means and controllable means for magnetizing said second ferrimagnetic means axially of said waveguide means for effecting a controllable phase shift of said circularly polarized wave energy, the improvement comprising control means for controlling the magnetization of said first ferrimagnetic means, and circuit means for energizing said control means, said circuit means comprising variable means for changing said magnetization of said first ferrimagnetic means in response to a change in a condition tending to degrade said conversion from linear to circular polarization.
 2. The improvement of claim 1 wherein said circular polarizer means comprise a transversely magnetized quadrupole field nonreciprocal circular polarizer.
 3. The improvement of claim 2 wherein said variable means comprise preprogrammed means responsive to a change from one preselected wave energy frequency to another preselected wave energy frequency.
 4. The improvement of claim 2 wherein said variable means are temperature responsive.
 5. The improvement of claim 2 wherein said variable means comprise sensor means in said waveguide means for sensing divergence from a desired polarization of said wave energy.
 6. The improvement of claim 5 including a linear polarizer on the side of said circular polarizer means away from said phase shifter means, said linear polarizer comprising absorptive means for absorbing wave energy polarized normal to a desired plane of polarization, said sensor means comprising means operatively connected to said absorptive means.
 7. The improvement of claim 6 wherein said absorptive means comprise a resistive film and said sensor means comprise a diode in contact with said film.
 8. The improvement of claim 2 wherein the waveguide is square in cross section.
 9. The improvement of claim 2 wherein said first and second ferrimagnetic means comprise a single rod.
 10. The improvement of claim 1 including second circular polarizer means including third ferrimagnetic means in said waveguide means for converting said phase shifted circularly polarized wave energy to linearly polarized wave energy, said phase shifter means being disposed between said first and second circular polarizer means.
 11. The improvement of claim 10 wherein said first and second circular polarizer means comprise transversely magnetized quadrupole field nonreciprocal circular polarizers.
 12. The improvement of claim 11 wherein said control means control the magnetization of both said first and third ferrimagnetic means.
 13. The improvement of claim 12 wherein said variable means comprise sensor means in said waveguide means for sensing divergence from a desired polarization of said wave energy.
 14. The improvement of claim 13 including a linear polarizer on the output side of said second circular polarizer means, said linear polarizer comprising absorptive means for absorbing wave energy polarized normal to a desired plane of polarization, said sensor means comprising means operatively connected to said absorptive means.
 15. The improvement of claim 11 wherein said first, second and third ferrimagnetic means comprise a single rod. 